The present invention relates to optical waveguides and wave-guiding components and, more particularly, to a process for fabricating optical waveguides and components in a substrate material using ion implantation and further processing of the substrate to create optical waveguide and waveguide components of controllable phase velocity. The invention also relates to various optical wave-guiding components or elements produced by this process.
The guiding structure in optical waveguide elements such as optical fibers is a region of relatively high index of refraction surrounded by a region of lower index of refraction. Because of the lowered phase velocity in the central region or core of high index of refraction, the energy density in the surrounding, lower index region decays exponentially, effectively confining all the light energy to the immediate region of the hiqh index core. The core thus acts as a light guiding region and the surrounding region acts as a light containing or confining region, thus providing wave-guiding properties with little loss.
Such structures are used increasingly in the field of signal transmission, particularly communications, for guiding information-carrying light from one location to another. The ability to guide the light with little loss is, of course, an important aspect of optical waveguide systems. In addition, it is important to be able to perform a variety of functions on the light traversing an optical waveguide system, such as mixing, splitting, attenuating, sampling, and detecting.
The present invention provides a novel process for fabricating optical wave-guiding components in a substrate, particularly a silicon substrate. Using the present techniques, a variety of optical wave-guiding components such as waveguides, directional couplers, attenuators, detectors and terminations can be readily fabricated. As will be seen hereinafter, the use of ion implantation and other known integrated circuit fabrication techniques permits the creation of optical waveguide of controllable phase velocity which can be configured to provide this wide variety of optical components.